Dirt Rag’s first test-ride on Shimano’s electronic XTR Di2: Part 2

This is Part 2 of my first real shakedown rides with the new Shimano XTR Di2 group. Read Part 1 here.

In the span of just a few days since receiving the goods I was able to put almost 150 off-road miles on Shimano’s exciting new XTR Di2 electronic components. Here’s a rundown of how it went in the California and Arizona desert.

Synchro Shifting

Yes indeed, automatic shifting and double chainrings, that’s what XTR Di2 is all about. At first mention it’s also perhaps becoming one of the most polarizing features in mountain bike drivetrain history—until you try it. Many riders initial reaction upon hearing about Synchro Shifting is concern over a loss of control over gear selection resulting in unwanted shifts and/or being in the wrong gear at the wrong time. I can tell you that over all those miles I mentioned earlier that never happened. Not once. The truth is as a rider you still have plenty of control over gear selections and the system actually enhances control and certainly increases the speed of gear selection and shifting

Synchro Shift is controlled by the handlebar mounted display unit that serves as the brain. There are three settings: S1 for race style riding, S2 for “trail” riding and manual, which turns off Synchro Shift (a setting I couldn’t use because I didn’t have a front derailleur shifter plugged in.) Besides controlling shift settings the unit displays current rear gear by number, shows battery life, and serves as the recharge and computer port. It can also display and control suspension mode if you have Fox’s electronic iCD suspension plugged in. The battery is the same as Di2 on the road and is mountable in various positions depending on bike frame. In the case of the Di2 specific Pivot Mach 429 SL, it’s integrated and hidden in the frame, as are all the wires.

Plug and play

As I mentioned in my first report, the dynamics of performance can be easily altered via a downloadable computer program. When the display until is plugged into a computer the entire system shows up on the screen with all your options including yes or no for the front shifter, suspension, gear ratios related to when it auto shifts and shift speed.

My changes, besides reversing which button up and down shifted to match the mechanical version, were essentially beefing up the stock S1 and S2 with S1 being based around racing with more time in the big ring and S2 being based around trail riding with more time in the inner ring (both of which, according to the Shimano tech that came up with the custom mapping, makes it feel like 13 gears in the back rather than 11.) I also increased rear derailleur shift speed when holding down the shift button (hold it down and the chain can dance across the entire cassette quicker than you can blink.) The cool thing is because it’s so easy to program you can search for your own settings or just leave it stock which ultimately works amazing—the tinkerer in me just had to be able to say I changed it a bit I guess.

Because it’s so programmable, you can customize deeper by running both shifters and having both control rear shifting, or make one side all upshift and the other all downshift. If you choose to go with Fox’s iCD suspension rather than using the stock Fox button you could program the front shifter to control the fork and shock lockout. Or, set it to manual, leave both shifters on and just enjoy great shifting that way. The one fly in the soup is that thus far Shimano is resisting to make it Mac compatible. Also, making it mobile Android and iOS compatible would be a great thing.

Battery life is less than the road version mainly due to the rear derailleur having to push inward against the clutch mechanism. Expect to get about 20 hours based on how much you shift and temperatures–Shimano Skunk riders did the entire seven day BC Bike Race on one charge. If the battery did begin to die on the trail you’ll lose front shifting ability first followed by rear with it staying in whatever gear you were in when it finally puckers out.

On the trail

Since using XTR Di2 I can say I’ve never used a front shifter with the system and I never will, Synchro Shift is that good. My initial concerns of suddenly being in the wrong gear or getting frustrated with auto shift simply never materialized. As you shift through the cassette you’ll hear a double beep to signal on the next rear shift that the front will be auto shifting and the rear will be dropping up or down a few gears to compensate.

It worked perfectly every time and after just a few miles I was able to anticipate the shift and adjust cadence like I would if I was doing the shift manually except if you tried shifting both front and rear in the same fashion with a cable system you’re risking a jammed or derailed chain—something that has never happened yet with XTR Di2 no matter how sloppy my shift and pedaling form became. I was also always in the right gear at the right time. In fact, I’ve begun to ride (and think) like it’s a single ring in front, the performance of the double ring auto shift is that spot on, intuitive and seamless.

Other performance notes include a nice tactile feel at the shifter. Rather than just being buttons the triggers move just enough to give you a solid feel of shifting. This also prevents accidental shifts. I would like to see more lever position adjustability. At times they seemed to close together and I’d occasionally over extend my thumb and push the wrong trigger. I’ve moved the shifter perch farther inward on the bar as a fix.

Because the 11-40 cassette is designed around double (36/26 chainrings) and even triple setups rather than a single ring (though that is an option) the steps between gear ratios is noticeably tighter than that of SRAM’s 11-speed cassette and as such I found myself shifting a lot more and staying right in the gearing sweet spot everywhere on the trail

Final thoughts

Undeniably Shimano has hit a home run with electronic mountain bike shifting. It’s also essentially the same weight as mechanical XTR—a feat Shimano says it achieved because the electronic wires are so much lighter than cables and housing. Price is, as you’d expect: about $3,300 to $3,500 for the complete group including brakes. But as with the Di2 systems for the road you can expect to see it trickle down to at least XT level in the future for a substantial cost savings.

Kudos to Shimano for setting up ride sessions in the tough, rocky terrain of Palm Springs to showcase durability. There were many times squeezing though rock sections at speed where I expected to snag or bang the rear derailleur but it never happened. I left with a few small scrapes on my cranks as a reminder of how unforgiving the desert can be but ultimately there were zero failures or broken parts. As you may have noticed, I haven’t got much to complain about yet.

Now it’s on to long-term east coast testing. Keep an eye on dirtragmag.com for more!